It is often desired to provide tires for vehicles that can be operated in a deflated condition for a suitable distance at a desired speed. The purposes have been varied, ranging from a desire to eliminate a vehicular spare tire so that its occupied space could be more efficiently used for other purposes and, also, a desire to enable a vehicle to remain operable even with a punctured pneumatic tire for a suitable time or distance whether or not a spare tire is available.
In some instances, such objectives have been proposed to be accomplished by providing a multiple chambered tire and also by positioning a run-flat device within the tire-wheel cavity to prevent the tire, upon an appreciable loss of internal inflation pressure, from going completely flat. Such run-flat devices can be substantially rigid in nature and prevent a total collapse of the tire by supporting the tire's inner surface in its crown region in proximity of the ground contacting portion. In such condition, the tire is prevented from going flat against its rim and, moreover, substantially retains its inflated circumferential shape and enables its vehicle to continue its travel over a more reasonable distance.
Examples of various tire assemblies might be visualized with their mechanical features in British Pat. Nos. 1,359,469 and 835,334 and U.S. Pat. No. 3,828,836.
However, it is considered necessary to provide lubricity at the interface between the run-flat device and a collapsing tire's inner surface in order to retard or reduce an attendant potential frictional, destructive heat build up at the tire's inner surface. Accordingly, it is often desired to provide a lubricant for such innerface.
A lubricant for tires containing internal run-flat devices is described in U.S. Pat. No. 4,036,765 as being a gel which is essentially solid or non-flowing at a tire's operating temperature such as below 70.degree. C. but becomes flowable at 90.degree. C. or higher. Such lubricant composition is described as comprising selected amounts of a fatty acid, an alkali or alkaline metal soap and a carrier in which the soap has appreciable solubility but the fatty acid is essentially insoluble. The carrier is described as being comprised of at least one of polypropylene ether glycol/triol, polyethylene ether glycol/triol and water and ethylene glycol and its lower homologs.
Although the gel of U.S. Pat. No. 4,036,765 is satisfactory for many purposes, and has been observed that, in order to provide sufficient lubricity, it remains desired to provide a lubricant of adequate lubricity which is not corrosive toward some types of metallic run-flat devices which are positioned within the pneumatic tire cavity to prevent the tire from going completely flat upon reduction of its internal pressure.